Some new designs of mobile communication devices—such as smart phones, tablet computers, and laptop computers—contain multiple Subscriber Identity Module (SIM) cards that provide users with access to multiple separate mobile telephony networks. Examples of mobile telephony networks include GSM, TD-SCDMA, CDMA2000, and WCDMA. Example multi-SIM mobile communication devices include mobile phones, laptop computers, smart phones, and other mobile communication devices that are able to connect to multiple mobile telephony networks. A mobile communication device that includes a plurality of SIMs that share a radio-frequency (RF) resource for communicating with their respective mobile telephony networks and connects to multiple separate mobile telephony networks is termed a “multi-SIM-multi-standby communication device” or “MSMS communication device.” An example is a dual-SIM dual standby (DSDS) device.
A MSMS communication device may include one or more shared RF resources that the multiple subscriptions use to communicate with their respective mobile telephony networks. However, only one subscription may use each RF resource to communicate with its mobile network at a time. Even when a subscription is in “standby” mode, meaning it is not currently actively communicating with the network, it may still need to perform discontinuous reception (DRX) operations to receive network paging messages at regular intervals (i.e., a discontinuous reception period) in order to remain connected to the network. Paging intervals for different subscriptions are not necessarily the same nor are they synchronized. Therefore, it is possible that at a certain times, the multiple subscriptions sharing an RF resource may need to use the RF resource to communicate with their respective mobile networks simultaneously. For example, two subscriptions out of three or more subscriptions may try to use a single RF resource to receive their paging messages simultaneously, or one subscription may be using the RF frontend when another other subscription is scheduled to receive a network paging message.
A “page collision” occurs when page reception times of two or more subscriptions overlap, as happens when the network paging messages for multiple subscriptions are scheduled at the same time. When a page collision occurs, one subscription must be assigned the RF resource to the exclusion of the other subscriptions. In other words, one subscription may block the other subscriptions from communicating with their respective networks (i.e., not receive their schedule page messages). Currently, the paging DRX cycle length (i.e., the length of time from the beginning of one network paging session to the next) for each subscription is determined entirely by the network and occurs in regular, predictable intervals. MSMS communication devices cannot manipulate or reschedule the paging DRX cycle for the multiple subscriptions and, therefore, cannot prevent page collisions from occurring between the multiple subscriptions even though page collisions can be anticipated. These page collisions may greatly affect mobile terminal call success rates of MSMS communications devices, especially when page collisions between two or more subscriptions are persistent.